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# ⚠️ Breaking Many deprecated queue config options are removed (actually, they should have been removed in 1.18/1.19). If you see the fatal message when starting Gitea: "Please update your app.ini to remove deprecated config options", please follow the error messages to remove these options from your app.ini. Example: ``` 2023/05/06 19:39:22 [E] Removed queue option: `[indexer].ISSUE_INDEXER_QUEUE_TYPE`. Use new options in `[queue.issue_indexer]` 2023/05/06 19:39:22 [E] Removed queue option: `[indexer].UPDATE_BUFFER_LEN`. Use new options in `[queue.issue_indexer]` 2023/05/06 19:39:22 [F] Please update your app.ini to remove deprecated config options ``` Many options in `[queue]` are are dropped, including: `WRAP_IF_NECESSARY`, `MAX_ATTEMPTS`, `TIMEOUT`, `WORKERS`, `BLOCK_TIMEOUT`, `BOOST_TIMEOUT`, `BOOST_WORKERS`, they can be removed from app.ini. # The problem The old queue package has some legacy problems: * complexity: I doubt few people could tell how it works. * maintainability: Too many channels and mutex/cond are mixed together, too many different structs/interfaces depends each other. * stability: due to the complexity & maintainability, sometimes there are strange bugs and difficult to debug, and some code doesn't have test (indeed some code is difficult to test because a lot of things are mixed together). * general applicability: although it is called "queue", its behavior is not a well-known queue. * scalability: it doesn't seem easy to make it work with a cluster without breaking its behaviors. It came from some very old code to "avoid breaking", however, its technical debt is too heavy now. It's a good time to introduce a better "queue" package. # The new queue package It keeps using old config and concept as much as possible. * It only contains two major kinds of concepts: * The "base queue": channel, levelqueue, redis * They have the same abstraction, the same interface, and they are tested by the same testing code. * The "WokerPoolQueue", it uses the "base queue" to provide "worker pool" function, calls the "handler" to process the data in the base queue. * The new code doesn't do "PushBack" * Think about a queue with many workers, the "PushBack" can't guarantee the order for re-queued unhandled items, so in new code it just does "normal push" * The new code doesn't do "pause/resume" * The "pause/resume" was designed to handle some handler's failure: eg: document indexer (elasticsearch) is down * If a queue is paused for long time, either the producers blocks or the new items are dropped. * The new code doesn't do such "pause/resume" trick, it's not a common queue's behavior and it doesn't help much. * If there are unhandled items, the "push" function just blocks for a few seconds and then re-queue them and retry. * The new code doesn't do "worker booster" * Gitea's queue's handlers are light functions, the cost is only the go-routine, so it doesn't make sense to "boost" them. * The new code only use "max worker number" to limit the concurrent workers. * The new "Push" never blocks forever * Instead of creating more and more blocking goroutines, return an error is more friendly to the server and to the end user. There are more details in code comments: eg: the "Flush" problem, the strange "code.index" hanging problem, the "immediate" queue problem. Almost ready for review. TODO: * [x] add some necessary comments during review * [x] add some more tests if necessary * [x] update documents and config options * [x] test max worker / active worker * [x] re-run the CI tasks to see whether any test is flaky * [x] improve the `handleOldLengthConfiguration` to provide more friendly messages * [x] fine tune default config values (eg: length?) ## Code coverage: 
63 lines
1.4 KiB
Go
63 lines
1.4 KiB
Go
// Copyright 2023 The Gitea Authors. All rights reserved.
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// SPDX-License-Identifier: MIT
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package queue
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import (
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"context"
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"time"
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)
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const (
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backoffBegin = 50 * time.Millisecond
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backoffUpper = 2 * time.Second
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)
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type (
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backoffFuncRetErr[T any] func() (retry bool, ret T, err error)
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backoffFuncErr func() (retry bool, err error)
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)
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func backoffRetErr[T any](ctx context.Context, begin, upper time.Duration, end <-chan time.Time, fn backoffFuncRetErr[T]) (ret T, err error) {
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d := begin
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for {
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// check whether the context has been cancelled or has reached the deadline, return early
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select {
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case <-ctx.Done():
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return ret, ctx.Err()
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case <-end:
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return ret, context.DeadlineExceeded
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default:
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}
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// call the target function
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retry, ret, err := fn()
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if err != nil {
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return ret, err
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}
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if !retry {
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return ret, nil
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}
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// wait for a while before retrying, and also respect the context & deadline
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select {
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case <-ctx.Done():
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return ret, ctx.Err()
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case <-time.After(d):
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d *= 2
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if d > upper {
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d = upper
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}
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case <-end:
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return ret, context.DeadlineExceeded
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}
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}
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}
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func backoffErr(ctx context.Context, begin, upper time.Duration, end <-chan time.Time, fn backoffFuncErr) error {
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_, err := backoffRetErr(ctx, begin, upper, end, func() (retry bool, ret any, err error) {
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retry, err = fn()
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return retry, nil, err
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})
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return err
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}
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